Substituted glycines

ABSTRACT

A new process is disclosed for the preparation of N-acyl- Alpha -aromatic and N-acyl- Alpha -heteroaromatic glycines by reaction of an Alpha -ester or ether of an N-acylglycine ester or acid with an aromatic or heteroaromatic compound. Also disclosed are new intermediates for preparing N-acyl- Alpha -aromatic and Nacyl- Alpha -heteroaromatic glycines.

United States Patent [1'91 Gleason et a1.

[451 Nov. 18, 1975 SUBSTITUTED GLYCINES [75] Inventors: John G. Gleason, Cornwall Heights,

Pa; Kenneth G. Holden, Haddonfield, N.J.; Nelson C. F. Yim, Philadelphia, Pa.

[73] Assignee: Smithkline Corporation,

Philadelphia, Pa.

[22] Filed: Feb. 28, 1974 [21] Appl. No.: 447,468

[56] References Cited UNITED STATES PATENTS 2,508,249 5/1950 Gleim 260/482 C heteroaromatic glycines.

2,856,386 10/1958 Smith et al...... 260/482 C 2,954,396 9/1960 Ayers et a1 260/482 C 3,078,301. 2/1963 T aub 260/482 C 3,079,302 2/1963 Bergel et al 260/482 C Primary Examiner.lames A. Patten Assistant ExaminerKillos Attorney, Agent, or Firm.lanice E. Williams; Alan D.

- Lourie; William H. Edgerton ABSTRACT A new process is disclosed for the preparation of N- acyl-a-aromatic and N-acyl-a-heteroaromatic glycines by reaction of an a-ester or ether of an N-acylglycine I ester or acid with an aromatic or heteroaromatic compound. Also disclosed are new intermediates for preparing N-acyl-a-aromatic and N-acyl-a- 5 Claims, No Drawings SUBSTITUTED GLYCINES' This invention relates to a process for preparing N- acyl-a-aromatic and N-acyl-a-heteroaromatic glycines .and to intermediates for preparing said compounds. In

In the above formulas l-lll, R'Y is any group which with the adjacent carbonyl group forms an amine protective group removable under conditions which are mild enough not to affect the remainder of the m'olecule. R can therefore be straight or branched chain lower alkyl of one to four carbon atoms, B-,B,B-trichloroethyl or substituted or unsubstituted benzyl. Y can be or S. The substituents on benzyl can be halo, alkyl, alkoxy or nitro. Preferred groups are those where RY is tbutoxy, [3,13,3-trichloroethoxy and benzyloxy.

ZR is any ester or ether group readily replaceable by an electron-rich aromatic or heteroaromatic group. Z can therefore be 0, S or 2 droxy, mercapto, nitro or amine groups, or any other groups that do not by their reactivity or election-withdrawing character prevent the replacement reaction from proceedingsatisfactorily. The only certain limitation on the nature of the Ar group is that it must possess an unsubstituted position which can bond to the a-carbon atom of the glycine molecule.

When used herein, the terms lower alkyl, lower alkoxy and flower alkanoyl are intended to refer to straight or branched chain groups containing from one to four carbon atoms. The term halo is intended to refer to fluoro, chloro, bromo and iodo.

and R can be straight or branched chain lower alkyl of one to four carbon atoms; halomethyl such as trifluoromethyl; aryl such as phenyl, which may be unsubstituted or substituted with one or two halo, lower alkyl, hydroxy, lower alkoxy, nitro, amino or acetamido groups; or aralkyl such as benzyl, which may beunsubstituted or substituted in the same manner as phenyl. Preferred groups are those where ZR is lower alkanoyloxy such as i f) O JCH;

(acetoxy), lower alkoxy such as OCT-i (methoxy) and OCJ-l, (butoxy), SCl-l C H (benzylthio), OC H (phenoxy) and lower alkylthio such as SCI-I (methylthio).

R is hydrogen, exceptwhen ZR is phenoxy, or any carboxyl protective group which is easily removable or is itself usable in the acylation reaction in which the product glycine compound is used. R can therefore be hydrogen, except when ZR is phenoxy, straight or branched chain lower alkyl of one to four carbon atoms, haloalkyl such as B,B,B-trichloroethyl, benzyl or substituted benzyl such as p-nitrobenzyl or p-methoxybenzyl. In addition, R can be any activated ester known to the art to be usable for the acylation of peptides, penicillins or cephalosporins.

Ar can be any aromatic or'heteroaromatic group that is sufficiently electron-rich to replace the ZR? group.

can be unsubstituted or substituted with one or two lower alkyl, lower alkoxy, lower alkylthio halo, hy-

N-Acyl-a-aro matic and N-acyl-a-heteroaromatic glycines are intermediates useful for preparing antibacterial aromatic and heteroaromatic glycinamidopenicillins and cephalosporins. Examples of such antibacterial compounds are described in US. Pat. Nos. 2,985,648, 3,507,86l and 3,560,489 and Belgian Pat. No. 784,995. The penicillins and cephalosporins are prepared by acylation of the penicillin or cephalosporin nucleus with the aromatic or heteroaromatic glycine. Prior to the acylation reaction, the amino group of the glycine moiety is normally protected with any of a variety of well-known and easily-removed amine protective groups. Thus, one normally must prepare the aromatic or heteroaromatic glycine compound and then protect the amino group prior to the acylation reaction. The advantage of the present process is that the protection of the amino group can be accomplished in the same reaction in which the aromatic or heteroaromatic glycine is itself prepared.

The process of this invention whereby the ZR leaving group is replaced by the Ar group is carried out by combining the a-ester or ether of formula I with at least an equimolar amount of the aromatic or heteroaromatic compound (Ar). The reaction is generally carried out using an acid catalyst, including Lewis acids, among which boron trifluoride as its etherate, aluminum chloride, formic acid and trifluoroacetic acid are preferred. Highly election-rich aromatic reactants such as indole, purine and pyrrole require no catalyst. When the aromatic moiety is insufficiently election-rich to replace the a-ester orether, even with an acid catalyst, it

is used as a metal salt. Thus, when Ar isphenyl, the reaction is best carried out using phenyl lithium as a reactant. When the leaving group (2R is a thioether, mercuric acetate is used in'addition to the acid catalyst.

The reaction is carried out in the liquid phase. A solvent is generally preferred; among those being usable are such non-polarorganic solvents as benzene, toluene, xylene, carbon-tetrachloride, ethyl acetate, dioxane, tetrahydrofuran, ether, methylene chloride and chloroform. The aromatic reactant may be employed in v thin layer chromatography. This time will vary from approximately 15 minutes-to 24 hours. In cases where an aromatic moiety .is sluggish in reacting, high temperatures, including. those reached only by heating in the absence of solvent, may be required. The product is thenisolated and purified according to standard meth- 3 ods, including solvent extraction, chromatography and recrystallization.

The esters of formula III obtained by this process may be hydrolyzed or used directly in acylating penicillin and cephalosporin intermediates by well-known methods. Use of a base such as sodium bicarbonate or sodium carbonate in aqueous methanol or dioxane is preferred for hydrolysis.

The compounds of formula I which are reacted with the aromatic nuclei to give compounds of formula 111 are themselves prepared by condensing an amide of formula IV, a glyoxylic ester or formula v and an acid, alcohol or mercaptan of formula VI, as shown below:

(IT ICI) ZR RYCNH HCCOOR HZR RYCNHCHCOOR 1V V VI 1 An anhydride may be used instead of an acid. R,R ,R ,Y and Z are as defined above. This reaction is carried out either using one of the reactants as a solvent or in an organic solvent such as dioxane, benezene, xylene or toluene. The temperature of the reaction will vary with the reactants, but it is preferable to carry it out at the reflux temperature of the solvent unless lower temperatures are necessary to prevent serious decomposition.

Compounds of formula I where ZR is acyloxy are new and are considered part of the present invention. Among the preferred compounds of this group are those where RY is t-butoxy, [3,B,,Btrichloroethoxy or benzyloxy; R is hydrogen or lower alkyl and ZR is lower alkanoyloxy. The p-nitrobenzyl and p-methoxybenzyl glyoxylic acid esters are prepared according to known procedures, for example, by treating glyoxylic acid with a p-nitrobenzyl or p-methoxybenzyl halide in the presence of base.

It will be recognized that, due to the asymmetric ozcarbon atom in the glycine compounds of formulas 1 and 111, optical isomers will exist. The resolved glycines are readily obtained, when desired, by resolution of the racemic compounds by well-known methods including fractional crystallization of a salt formed with an optically active acid or base. Both the resolved and racemic compounds are usable and obtainable in the process of the invention and both are comprehended by the definition of the claimed intermediate glycines.

Many examples of a-substituted N-acylglycines and glycine esters are found in the prior art. Various (1- alkoxy-N-benzoylglycines and glycine esters are described in Zhur. Obshch. Khim. 25, 1360 (1955), Bull. Soc. Chim. Fr., 530 (1959), Doklady Akad. Nauk. S.S.S.R., 106,675 (1956) and 137, 1377 (1961) and Nippon Kagaku Zasshi, 76, 1022 (1955). N-Phenylacetyl-a-methoxyglycine is disclosed in U.S. Pat. 2,523.621, while N-phenylacetyl-a-benzyloxyglycine is described in Experientia, 21, 317 (1965). The corresponding methyl and benzyl esters are found in .1. Chem. Soc. C, 14, 1264 (1967) and Ann. Chim (Rome), 60, 259 (1970), respectively.

Huisgen and Blaschke have prepared N-ethoxycarbonyl-a-benzoylglycine ethyl ester [Chem. Ber., 98, 29585 (1965)]. The preparations of a-hydroxy, atamino (for example, unsubstituted and substituted anilino, benzylamino and morpholino) and a-halo N- ethoxycarbonyl, N-benzoyl and N-phenylacetylglycine 4 esters are described by MatthiesIPharmazie, 25, 522 1970)]. 7

Synthesis of N-a-alkoxybenzylbenzamides is described in Tetrahedron, 23, 286977 (1967). Synthesis of an a-carbethoxyiminoacetic ester and conversion to an N-acyl-a-indolylglycine ester are described in Tetrahedron Letters No. 41, 4371-73 (1968). Synthesis of glycines by means ofa Grignard reaction is described in Tetrahedron Letters No. 21, 1813-16 (1970).

Other references may exist describing compounds similar to those described in the above references. However, the inventors are aware of no disclosure of N-acyl-a-acyloxyglycines or of their use in preparing N-acyl-a-aromatic or heteroaromatic glycines.

The following examples illustrate the products and processes of the invention, but are not to be construed as limiting the scope thereof. Temperatures are in degrees Centrigrade unless otherwise stated.

EXAMPLE 1 N-t-Butoxycarbonyl-Z-acetoxyglycine N-butyl ester A solution of 23.4 g. (0.2 mol.) of t-butyl carbamate [Org. Syn., 48, 32 (1968); US. Pat. No. 3,072,710] and 32.2 g. (0.25 mol.) of n-butyl glyoxylate (Org. Syn., Col. Vol. 4, 124) in 150 m1. of acetic anhydride was refluxed for 1.25 hours. The reaction mixture was then cooled, the solvent was removed in vacuo and the residue was molecularly distilled at /.O5 mm. to give the title compound.

Use of formic, propionic or butyric anhydride in place of the acetic anhydride gives the corresponding 2-formyloxy, 2-propiony1oxy or 2-butyryloxy compound, respectively.

EXAMPLE 2 N-(B,B,B-Trichloroethoxycarbonyl )-2-acetoxyglycine n-butyl ester When 38.5 g. of B,B,B-trichloroethyl carbamate (U.S. Pat. No. 3,072,710) was substituted in the procedure of Example 1 for t-butyl carbamate, the title compound was obtained.

EXAMPLE 3 Substitution of 22.6 g. of benzyl carbamate in the procedure of Example 1 for t-butyl carbamate gave N- benzyloxycarbonyl-2-acetoxyglycine n-butyl ester.

By similar use of p-methoxybenzyl carbamate and pnitrobenzyl carbamate in the procedures described herein, there are prepared the corresponding N-(pmethoxyand p-nitrobenzyloxycarbonyl)glycines of this invention.

EXAMPLE 4 N-Benzyloxycarbonyl-Z-n-butoxyglycine n-butyl ester A solution of 3.0 g. (0.02 mol.) of benzyl carbamate, 1.8 g. (0.02 mol.) of glyoxylic acid hydrate and 0.1 g. of p-toluenesulfonic acid in 50 m1.of n-butanol was slowly distilled over a one hour period. The last of the solvent was removed in vacuo to give a residue which was dissolved in hexane and filtered to remove the p-toluenesulfonic acid. The filtrate was chromatographed on alumina (Woelm. activity 11) and eluted with hexane. Concentration of the eluate in vacuo and molecular distillation of the residue at 130/0.1 mm. gave the title compound.

EXAMPLE 7 N-Benzyloxycarbonyl-2-methoxyg1ycinev methyl ester A solution of 3.0 g. (0.02 mol.) of benzyl carbamate 5 EXAMPLE 6 N-t-Butoxycarbonyl-2-phenoxyglycine n-butyl ester To 2.9 g. (0.01 mol.) of N-t-butoxycarbonyl-Z- acetoxyglycine n-butyl ester in 10 ml. of dioxane was added a solution of sodium phenolate prepared from 0.94 g. of phenol and 0.54 g. of sodium methoxide in ml. of dioxane. After refluxing for 2 hours, the solvent was evaporated in vacuo and the residue was *dissolved in ethyl acetate. The ethyl acetate solution was washed with cold 10% aqueous sodium hydroxide, dried (MgSO and concentrated to yield the title compound as an oil.

Alternatively, N-t-Butoxycarbonyl-2-phenoxyglycine n-butyl ester was prepared by heating a mixture of 1.5 g. (0.005 mol.) of N-t-butoxycarbonyl-2-acetoxyglycine n-butyl ester and 0.5 g. (0.005 mol.) of phenol at 150 for 1 hour. The residue was dissolved in ethyl acetate and the resulting solution was washed with cold 10% aqueous sodium hydroxide, dried (MgSO and concentrated to give the title compound.

EXAMPLE 7 N-Benzyloxycarbonyl-Z-S-benzylthioglycine A mixture of 15.1 g. (0.1 mol.) of benzyl carbamate, 7.4 g. (0.1 mol.) of glyoxylic acid hydrate and 24.0 g. (0.1 mol.) of benzyl mercaptan in 100 ml. of toluene was refluxed for 0.5 hour. After cooling, the reaction mixture was filtered and the crystalline product was washed with toluene, dried in vacuo and recrystallized from ethyl acetate-hexane to give the title compound, m.p. l20-l22.

EXAMPLE 8 N-t-Butoxycarbonyl-2-S-methylthioglycine When equivalent amounts of t-butyl carbamate and methyl mercaptan are substituted in the procedure of Example 7 for benzyl carbamate and benzyl mercaptan, respectively, the title compound is obtained.

EXAMPLE 9 When an equivalent amount of t-butyl thiocarbamate [J. Org. Chem. 28, 3421 (1963); U.S. Pat. No. 3,072,710] is substituted in the procedure of Example, 1 for t-butyl carbamate, N-t-butylthiocarbonyl-Z- acetoxyglycine n-butyl ester is obtained. 1

Similarly, substitution of an equivalent amount of' n-butyl benzyl thiocarbamate [.I. Amer. Chem. Soc., 82, 458 2 (1960)] in the procedure of Example 1 for t-butyl ear bamat ef give N benzylthiocarbonyl-2 acetoxyglycine "i n-butyl ester.

EXA PLE 10 P N-B enzylthiocarbonyl-2-n-,butoxyglycine n-butyl ester When an equivalent amount of benzyl thiocarbamate When an equivalent amount of benzylthioc'arbamate is substituted in the procedure of Example 5 for benzyl carbamate, the title compound is obtained.

EXAMPLE l2 N -t-butylthio carbon yl-2-phenoxyglycine n-butyl ester I Substitution ofan equivalent amount of N -t -butylth iocarbony]-2-acetoxyglycine n-butyl ester in the procedure of Example 6 for N-t-butyoxycarbonyl 2 acetoxyglycine n-butyl ester gives the title compound;

. EXAMPLE 13 v 5 N-Benzylthiocarbonyl-Z-S-benzylthioglycine When an equivalent amount of benzyl thiocarbamate is substituted in the procedure of Example 7 for benzyl carbamate, the .title compound is obtained.

v EXAMPLE 14 N t-Butylthiocarbonyl-2-S-methylthioglycine Substitution-of anl equivalent amount of t-butyl thiocarbamate in the procedure of Example 8 for t-butyl carbamate gives the title compound. l

EXAMPLE l5 v N-Benzyloxycarbonyl-2 n-butoxyglycine A solution of 0.002 mol. of N-benzyloxycarbonyl-Z- n-butoxyglycine n-butyl ester is stirred with 10 ml. of methanol and 10 ml. of 5% aqueous sodium bicarbonatesodium carbonate solution for 5 hours at 25. The reaction mixture. is then diluted with water and shaken with ethyl acetate. The layers are separated and the aqueous layer is acidified to pH 2.0 and extracted with ethyl acetate containing 10% ethanol. The extracts are dried (Na SO and concentrated in vacuo to give the title compound.

In like manner, the other N-alkoxycarbonyl and N- alkylthiocarbonyl glycine esters described herein may be converted to the corresponding acids.

EXAMPLE 16 When an equivalent amount of methyl glyoxylate [Synthesis, 544 1972)] is substituted in the procedure of Example 1 for n-butyl glyoxylate, N-t-butoxycarbonyI-Z-acetoxyglycine methyl ester is obtained.

In like manner, N-(B,B,B-trichloroethoxycarbonyl)- 2- ac etoxyglycine methyl ester is prepared by substitution of an equivalent amount of methyl glyoxylate in the procedure of Example 2 for n-butyl glyoxylate.

Similarly, substitution of an equivalent amount of methyl glyoxylate in the procedure of Example 3 for glyoxylate gives N-benzyloxycarbonyl-2- acetoxyglycine methyl ester.

7 Other glycine methyl esters may be prepared by substitution of methyl glyoxylate for n-butyl glyoxylate in the appropriate procedures.

EXAMPLE l7 Substitution of an equivalent amount of ethyl glyoxylate [Synthesis, 544 (1972)] in the procedure'of Example 1 for n-butyl glyoxylate gives N-t-butoxycarbonyl- 2-acetoxyglycine ethyl ester.

In like manner, when an equivalent amount of ethyl glyoxylate is substituted in the procedure of Example 2 for n-butyl glyoxylate, N-(B,B,B-trichloroethoxycarbonyl)-2-acetoxyglycine ethyl ester is obtained.

When an equivalent amount of ethyl glyoxylate is substituted in the procedure of Example 3 for n-butyl glyoxylate, N-benzyloxycarbonyl-Z-acetoxyglycine ethyl ester is obtained.

Other glycine ethyl esters may be similarly prepared by substitution of an equivalent amount of ethyl glyoxylate for n-butyl glyoxylate in the appropriate proce dure.

EXAMPLE 18 When an equivalent amount of B,B,B-trichloroethyl 4 glyoxylate [.I. Amer. Chem. Soc., 88, 852 (1966)] is substituted in the procedure of Example 1 for n-butyl glyoxylate, N-t-butoxycarbonyl-2-acetoxyglycine B,B,[3-trichloroethyl ester is obtained.

Similarly, substitution of an equivalent amount of B,B,B-trichloroethyl glyoxylate in the procedure of Example 2 for n-butyl glyoxylate gives N-(B,B,B-trichloroethoxycarbonyl)-2-acetoxyglycine B,B,B-trichloroethyl ester.

In like manner, when an equivalent amount of B,B-,B- trichloroethyl glyoxylate is substituted in the procedure of Example 3 for n-butyl glyoxylate, N-benzyloxycarbonyl-2-acetoxyglycine B,B,/3-trichloroethyl ester is obtained.

Likewise, other glycine B,/3,[3-trichloroethyl esters may be prepared by substitution of an equivalent amount of I3,B,B-trichloroethyl glyoxylate for n-butyl glyoxylate in the appropriate procedures.

EXAMPLE 19 Substitution of an equivalent amount of benzyl glyoxylate in the procedure of Example 1 for n-butyl glyoxylate gives N-t-butoxycarbonyl-2-acetoxyglycine benzyl ester. 7

In like manner, when an equivalent amount of benzyl glyoxylate is substituted in the procedure of Example 2 for n-butyl glyoxylate, N-(B,B,B-trichloroethoxycarbonyl)-2-acetoxyglycine benzyl ester is obtained.

When an equivalent amount of benzyl glyoxylate is substituted in the procedure of Example 3 for n-butyl glyoxylate, N-benzyloxycarbonyl-2-acetoxyglycine benzyl ester is obtained.

Other glycine benzyl esters may be similarly prepared by substitution of an equivalent amount of benzyl glyoxylate for n-butyl glyoxylate in the appropriate pro-- the above procedures gives the corresponding glycine p-methoxybenzyl and p-nitrobenzyl esters.

EXAMPLE 20 When an equivalent amount of N-t-butoxycarb ony ll- 2-acetoxyglycine methyl ester is substituted in the pro- 8 cedure of Example 6. N-t+butoxycarbonyl-2-phenoxyglycinc methyl ester is obtained. V

In like manner, N-t-butoxycarbonyl-Z-phenoxyglycine ethyl ester is obtained by substitution of an equivalent amount of N-t-butoxycarbonyl-2-acetoxyglycine ethyl ester inthe procedure of Example 6.

.Similarly, when an equivalent amount of Nt-butoxycarbonyl-Z-aceto xyglycine ,B,B,Btrichloroethyl ester isv substituted in the procedure of Example 6, N-tbutoxycarbonyl-Z-phenoxyglycine ,B,,B.B-trichloroethyl ester is obtained V EXAMPLE 21 N t-Butoxycarbonyl-2 phenylglycine n-butyl ester A solution containing 2.4 mmol. of phenyl lithium in benzene-ether was added dropwise at 7 8 under argon to a solution of 700 mg. (2.4 mmol.) of N-t-butoxycarbonyl-2-acetoxyglycine n-butyl ester in 15 ml. of dry ether. The mixture was stirred for 2 hours at 78, then for 1 hour at 25. The mixture was diluted with water, the layers werev separated and the ether layer was washed with water, dried (Na SO and concentrated in vacuo. The residue was chromatographed on silica gel with methylene chloride to give a crude product which was rechromatographed on basic alumina to give the title compound. I

' Use of 2'-formyloxy, 2"-propi onyloxy, or 2-butyryloxy starting materials gives the same product.

EXAMPLE 22 N-t Butoxycarbonyl 2-(4-methoxyphenyl)glycine A solution of 290 mg. (.1 mmol.) of N-t-butoxycarbonyl-2-acetoxyglycine n-butyl ester, 0.5 ml. of anisole and 3 drops of boron trifluorideetherate in 5 ml. of methylene chloride was stirred at 25? for four hours. The solvent was removed and :the residue was chromatographed on silica gel and eluted with 1:1 chloroform-hexane to give the title compound.

' EXAMPLE 23 N-t-Butoxycarbonyl-2 (2,4-dihydroxyphenyl)glycine To a stirred mixture of 11.0 g. (0.1 mol.) of resorcinoland. 24.7 g. (0.085 mol.) of N-t-butoxycarbonyl-2 acetoxyglycine n-butyl ester in 250ml. of methylene chloride. at 0 was added 1 of boron trifluoride etherate. The reaction mixture was allowed to warm to room temperature during a 30 minute period, then it was stirred for an additional 3 hours. The reaction mixture was washed five times'with equal volumes of water, dried (Na SO and concentrated in vacuo to give N-t-butoxycarbonyl-2-(2,4-dihydroxyphenyl)glycine n-butyl ester. v v

To a boiling solution of 23 g. (0.067 mol.) of N-tbutoxycarbonyl-2( 2,4-dihydroxyphenyl )glycine nbutyl ester in 300 ml. of methanol was slowly added a solution of 23 g. of sodium bicarbonate in 300 ml. of water.- During addition, the reactionmixture was kept under a nitrogen atmosphere and the methanol was allowed to distill from the mixture. When all the methanol had been distilled the mixture was cooled, adjusted to pH 7.0 with phosphoric acid and extracted with ethyl (Na SO and concentrated in vacuo to give the title compound.

N-t-Butoxycarbonyl-2-( 3-acetamido-4-hydroxy I pheny,l)glycine and N-t-butoxycarbonyl-'2-( 3-acetamido-2-hydroxyphenyl)glycine To a stirred mixture of 20.0 g. (0.069 mol.) of N -tbutoxycarbonyl-Z-acetoxyglycine n-butyl ester, 11 .5 g. (0.076 mol.) of 2-acetamidophenol and,200 ml. of methylene chloride was added 1 1.0 g. of boron trifluoride etherate under a nitrogen atmosphere. After 20 minutes the reaction mixture was shaken with sufficient aqueous sodium carbonate to bring the final pH of the aqueous phase to 7-8. The organic phase wasdried (Na SO and concentrated to give a residue which was hydrolyzed with sodium carbonate according to the procedure described in Example 23. The hydrolysis product, a mixture of N-t-butoxycarbonyl-2-(3- acetamido-4-hydroxyphenyl)glycine and N-t-butoxycarbonyl-2-(3-acetamido-2-hydroxyphenyl)glycine, was chromatographed on silica gel with 3:1 methylene chloride-ethyl acetate containing 1% acetic acid' followed by 2:1 ethyl acetate-acetone containing 1% acetic acid to effect separation of the compounds, m.p. l78l79 (4-hydroxy isomer from tetrahydrofuranhexane); m.p. l7 ll 72 (2-hydroxy isomer from ethyl acetate-hexane). I 1

EXAMPLE 25 a-(N-t-Butoxycarbonylamino)indole-3-acetic acid A solution of 20.2 g. (0.070 mol.) of N-t-butoxycarbonyl-2-acetoxyglycine n-butyl ester and 8.8 g. (0.075 mol.) of indole in 300 ml. of toluene was slowly distilled over a 30 minute interval with periodic replaceoxane was refluxed for 2.5 hours-The cooled reaction mixture was concentrated in vacuo and 30 ml. of water was added to the residue. The aqueous solution was extracted with methylene chloride, cooled and acidified to pH 2.0 with hydrochloric acid. The resulting solid was collected and recrystallized from ethyl acetate hexane to give the title compound, m.p. 143.5.

EXAMPLE-26 a-(N-t-Butoxycarbonylamino)purine-7-acetic acid n-butyl ester and a-(N-t-butoxycarbonylamino)-9H-purine-9-acetic acid n-butyl ester A mixture of 2.9 g. (0.01 mol.) of N-t-butoxycarbonyl-2-acetoxyglycine n-butyl ester and 1.2 g. (0.012 mol.) of purine was stirred under vacuum at 150-l 60 until cessation of acetic acid evolution.

The cooled reaction mixture was taken up in 20 ml. of methylene chloride and the solution was filtered.

Chromatography of the filtrate, containing a mixture of Y thetitle compounds, on 120 g. of silica '-gel with methylene chloride containing increasing amounts of acetone gave a'-( N-t-butoxycarbonylarnino )purin-7 -acetic acid, m.p. 135-l36 (acetone) and a-(N-t-butoxycarbonylamino)-9H -purine-9-acetic acid, m.p. l64165 (acetone g EXAMPLE 27 a-(N-t Butoxycarbonylamino)furan-Z-acetic acid n-butyl ester A solution of 1.6 g. (0.006 mol.) of N-t-butoxycarbonyl-2-acetoxyglycine n-butyl ester and 0.7 g. (0.01 mol.) 'of redistilled furan in ml. of methylene chloride was cooled'to -'78'and four drops of boron trifluoride etherate was added with stirring. The reaction mixture was warmed to room temperature and left for 3 hours. Chromatography on silica gel with methylene chloride and methylene chloride containing increasing amounts of ethyl acetate gave the title compound.

EXAMPLE 28 N t-Butoxycarbony1-2-(4-hydroxyphenyl)glycine and N-t-butoxycarbonyl-2 -(2-hydroxyphenyl)glycine A solution of .l .5 g. (0.005 mol.) of N-t-butoxycarbonyl-2-a 'cetoxy glycine n-butyl ester in 10 ml. of methylene chloride was slowly added over a one hour period to a stirred solution of 0.6 g. (0.006 mol.) of phenol and 0.1 ml. of boron trifluoride etherate in 15 ml. of methylene chloride. After 3 hours the reaction mixture was chromatographed'on 50g. of silica gel and eluted with methylene chloride containing increasing amounts of ethyl acetate to give N-t-butoxycarbonyl-2(4- ,hydroxyphenyllglycine n-butyl ester and N-t-butoxycarbonyl-2-(2-hydroxyphenyl)glycine n-butyl ester.

A solution of 0.5 g. 1.5 mmol.) of N-t-butoxycarbonyl-2- (4-hydroxyphenyl)glycine n-butyl ester in 20 m1. of methanol and 30 ml. of 5% aqueous sodium carbonate was heated at reflux for 30 minutes. The solvent was removed in vacuo and the aqueous residue was extracted with ethyl acetate. The aqueous phase was acidifie'd, to pH 3.0 with phosphoric acid and again extracted with ethyl acetate. The extract was dried (Na S0 and concentrated to give N-t-butoxycarbonyl-Z- (4-hydroxyphenyl)glycine, m.p. 1l'2-l 14 (methanolwater). i 1

Similarly, N-t-butoxycarbonyl-2-(2-hydroxyphenyl)glycine n-butyl ester was hydrolyzed to give N- t-butoxycarbonyl-2-(2-hydroxyphenyl)glycine, m.p. (methylene chloride-water). I

EXAMPLE 29 a-( N-t-Butoxycarbonylamino )pyrrole-Z-acetic acid n-butyl ester A solution of 14.5 g. (0.05 mol.) of N-t-butoxycarbonyl-2-acetoxyglycine n-butyl esterand 10 ml. of redistilled pyrrole in 75 ml. of toluene was slowly distilled with replacement of fresh toluene to maintain the volume at 50-75 ml. After 30 minutes the reaction mixture was cooled and concentrated in vacuo. The residue was dissolved in hexane and chromatographed on alumina (Woelm, activity II) with hexane-benzene followed by benzene to give the title compoung.

EXAMPLE 30 N -Be'nzyloxycarbonyl-2-( l-hydroxyphenyl)glycine and N-benzyloxycarbonyl-2-( 2-hydroxyphenyl )glycine Toa solution of 1.73 g. (0.010 mol.) of phenol and 0.2 ml. of boron trifluoride etherate in 20 ml. of methylenechloride was added'dropwise with stirring over a minute interval 3.37 g. (0.011 mol.) of N-benzyloxycarbonyl-2-acetoxyglycine n-butyl ester. After three hours the reaction mixture was cooled and the precipi tate collected by filtration to give N-benzyloxycarbony1-2-(4-hydroxyphenyl)glycine n-butyl ester, m.p.'

The filtrate was concentrated in vacuo and the residue was dissolved in benzene and chromatographed on silica gel. Elution with benzene containing increasing amounts of ethyl acetate gave N-benzyloxycarbonyl-2- (2-hydroxyphenyl)glycine n-butyl ester, m.p. 1 141 17 (ethyl acetate-hexane) and additional amounts of the 4-hydroxy isomer; I

By the same procedure, substitution of an equivalent amount of N-benzyloxycarbonyl-2-n-butoxyglycine nbutyl ester for N-benzyloxycarbonyl-2-acetoxyglycine n-butyl ester gave N-benzyloxycarbonyl-2-(4-hydroxyphenyl)-glycine n-butyl ester and N-benzyloxycarbonyl-2-(2-hydroxyphenyl)glycine n-butyl ester.

Hydrolysis of N-benzyloxycarbonyl-2-(4-hydroxyphenyl)glycine n-butyl ester as described in Example 29 gave N-benzyloxycarbonyl-2-(4-hydroxyphenyl)glycine, m.p. l88l90 (dec.). 1

Similarly, N-benzyloxycarbonyl-2-(Z-hydroxyphenyl)glycine n-butyl ester was hydrolyzed to give N- benzyloxycarbonyl-2-(2-hydroxyphenyl)glycine, m.p. 145- (dec.).

N-Benzyloxycarbonyl-2-(4-hydroxyphenyl)glycine was also obtained from treatment of a cold solution of 3.3 g. (0.01 mol.) of N-benzyloxycarbonyl 2-S-benzylthioglycine and 1.9 g. (0.02 mol.) of phenol in ml. of

methylene chloride with 1 ml. of boron'trifiuoride etherate and 6.4 g (0.02 mol.) of mercuric acetate. The

EXAMPLE 31 N-Benzyloxycarbonyl-2-(4-methoxyphenyl )glycine n-butyl ester V When an equivalent amount of N-benzyloxycarbo nyl-2-acetoxyglycine n-butyl ester was substituted in the procedure of Example 22 for N-t-butoxycarbonyl- 2-acetoxy glycine n-butyl ester, the title compound was obtained.

EXAMPLE 32 N-Benzyloxycarbonyl-2-(4-methylthiophenyl)glycine n-butyl ester A solution of 1.6 g. (5.0 mmol.) of N-benzyloxycan' bonyl-2-acetoxyglycine n-butyl ester, 1.0 g. (8.0 mmol.) of thioanisole and 10 drops of boron trifluoride etherate in 10 ml. of methylene chloride was stirred at for 2 hours. The reaction mixture was diluted with hexane and chromatographed on silica gel with hexane followed by 1:1 chloroform-hexane to give the title compound.

EXAMPLE 33 i1(N-Benzyloxycarbonylamino)thiophene-2-acetic acid n-butyl ester EXAMPLE 34 a-(N-Benzyloxycarbonylamino)pyrrole-2-acetic acid n-butyl ester Substitution of an equivalent amount of N-benzyloxycarbonyl-2-acetoxyg1ycine n-butyl ester in the procedure of Example 29 for N-t-butoxycarbonyl-2-acetoxyglycine n-butyl ester gave the title compound.

EXAMPLE 35 N-( 3,3,B-Trichloroethoxycarbonyl )-2-( 4-methoxyphenyl)glycine n-butyl ester A solution of 0.91 g. (3.0 mmol.) of N-(B,B,/3-trichloroethoxycarbonyl)-2-acetoxyglycine n-butyl ester and 0.3 g. (2.8 mmol.) of anisole in 20 ml. of methylene chloride containing two drops of boron trifluoride etherate was maintained at 25 for 5 hours. The solvent was then evaporated in vacuo and 2:1 hexane-methylene chloride was added. Chromatography on silica gel with methylene chloride containing increasing amounts of ethyl acetate gave the title compound.

Alternatively, the title compound was obtained by substitution of 10 ml. of toluene containing 0.3 ml. of trifluoroacetic acid in the procedure described above for methylene chloride and boron trifluoride etherate followed by refluxing the reaction mixture for 1.75 hours and chromotography as described.

EXAMPLE 36 N-(B,B,B-Trichloroethoxycarbonyl)-2-(4-hydroxy-3,5- dimethylphenyl)glycine n-butyl ester A solution of 1.8 g. (6 mmol.) of N-(B,B,B-trichloroethoxycarbonyl)-2-acetoxyglycine n-butyl ester and 1.2 g. (10 mmol.) of 2,6-dimethylphenol in 20 ml. of methylene chloride containing three drops of boron trifluoride etherate was stirred at 25" for 3 hours. The reaction mixture was concentrated in vacuo, 5 ml. of 2:1 hexanemethylene chloride was added and the resulting solution was chromatographed on silica gel. Elution with 2:1 hexanemethy1ene chloride then with methylene chloride containing increasing amounts of ethyl acetate gave the title compound. i

In like mannenthe title compound was prepared by substituting an equivalent amount of formic acid or trifluoroacetic acid in the procedure described above for methylene chloride and boron trifluoride etherate followed by refluxing the reaction mixture for 1 hour and chromatography as described.

EXAMPLE 37 a-( N-B,B,B-Trichloroethoxycarbonylamino)pyrrole-2- acetic acid When an equivalent amount of N-(B,B,B-trichloroethoxycarbonyl)-2-acetoxyglycine n-butyl ester was substituted in the procedure of Example 29 for N-t-butoxycarbonyl-Z-acetoxyglycine n-butyl ester, a-(N-B,B,B- trichloroethoxycarbonylamino)pyrrole-2-acetic acid n-butyl ester, m.p. l.5 (hexane) was obtained.

A suspension of 3.7 g. of the ester in 5% aqueous sodium bicarbonate and 200 ml. of methanol was stirred at 25 for 48 hours. The reaction mixture was concentrated in vacuo and the remaining aqueous solution was extracted with methylene chloride. The aqueous phase was cooled acidified to pH 3.0 with phosphoric acid and extracted with ethyl acetate. The extract was dried (Na SO and concentrated to give the title compound, m.p. 111 (hexane).

EXAMPLE 38 a-(N-B,B,B-Trichloroethoxycarbonylami'no)purine-7- acetic acid n-butyl ester When an equivalent amount of N-(B,B,B-trichloroethoxycarbonyl)-2-acetoxyglycine n-butyl ester was substituted in the procedure of Example 26 for N-t-butoxycarbonyl-2-acetoxyglycine n-butyl ester, the title compound was ultimately obtained, m.p.' l l4-1l6 (major product; acetone-hexane) We claim:

1. A compound of the formula:

or benzyl, the phenyl or benzyl group being unsubstituted or substituted with lower alkyl, lower alkoxy, hydroxy, halo, nitro or amino.

2. A compound as claimed in claim 1, where RY is t-butoxy, B,B,/3-trichloroethoxy or benzyloxy; ZR is acetoxy; and R is hydrogen or lower alkyl.

3. A compound as claimed in claim 2, being N-tbutoxycarbonyl-2-acetoxyglycine n-butyl ester.

4. A compound as claimed in claim 2, being N-benzyloxycarbonyl-2-acetoxyglycine n-butyl ester.

5. A compound as claimed in claim 2, being N- (B,B,B-trichloroethoxycarbonyl)-2-acetoxyglycine nbutyl ester.

G 7 UNITED STATES PATENT AND TRADEMARK OFFICE DATED November 18, 1975 Q Col. 1, line 65 "napthyl should read naphth l Q -N-t-butoxycarbonyl- Q Co1.l2, line 57 hexanemethylene should read -hexane-meth lene CERTIFICATE OF CORRECTION PATENT N0. 3,920,730

INVENTOR(S) John G. Gleason, Kenneth G. Holden, Nelson C.F. Yim

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[73] "Smithkline" should read SmithKline line 68 alkylthio halo," should read alkylthio, halo, Col. 3, line 12 "v" should read V line 23 "benezene" should read benzene C01. 4, line 22 "N-butyl should read n-butyl Col. 6, line 22 "N-t:--butyoxycarhorn;lshould read line 44 bonatesodium shouTd read Donate-sodium Co1.10, line 30 -2(4-- should read -2-(4- line 61 "compoung should read compound 001.11, line 19 "pheny1)g1ycine" should read pheny1)g1ycine line 28' "l r5 (dec.)" should read 145-148 (dec.)

line 59 "hexanemethylene should read --hexane-methylene Claim 1 in the definition of R "hydrogen lower alkyl, -halo(lower) alkyl" should read h d gen, lower alkyl, ha10(lower)al y Engncd and Sealed this twenty-fourth Day Of February 1976 [SEAL] Q Attest:

RUTH C. MASON C. MARSHALL DANN Atlesling Officer ('ummissimur uflatents and Trademarks O 

1. A COMPOUND OF THE FORMULA
 2. A compound as claimed in claim 1, where R1Y is t-butoxy, Beta , Beta , Beta -trichloroethoxy or benzyloxy; ZR3 is acetoxy; and R2 is hydrogen or lower alkyl.
 3. A compound as claimed in claim 2, being N-t-butoxycarbonyl-2-acetoxyglycine n-butyl ester.
 4. A compound as claimed in claim 2, being N-benzyloxycarbonyl-2-acetoxyglycine n-butyl ester.
 5. A compound as claimed in claim 2, being N-( Beta , Beta , Beta -trichloroethoxycarbonyl)-2-acetoxyglycine n-butyl ester. 